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Method for manufacturing magnetic sheet and magnetic sheet

a technology of magnetic sheets and magnetic sheets, applied in the direction of magnetic liquids, magnetic bodies, instruments, etc., can solve the problems of ferrite raising a problem on being fragile, extremely low impact resistance, and inability to ensure electric power, etc., to achieve high quality and high productivity

Inactive Publication Date: 2010-01-21
DEXERIALS CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0016]As a result of diligent study on manufacturing method of a magnetic sheet, the inventor of this application has discovered a method for manufacturing a magnetic sheet having a good appearance and magnetic characteristics with high productivity, and has accomplished this invention.
[0019]With the present invention, this method can solve a problem in which the magnetic sheets are accumulated in a misaligned state as in the conventional manufacturing method by accumulating and thermally compressing the plural magnetic sheets, can reduce air involved among the magnetic sheets. The present invention therefore can simplify the step of discharging the air by compression, improve the productivity, and suppress a problem in which the magnetic sheet changes its thickness due to air involved among the magnetic sheets under high temperature environment or high temperature and high humidity environment. The present invention further can manufacture the magnetic sheet with high magnetic permeability while maintaining an excellent appearance without leaving any scar due to air ejection even if compressed at a high-pressure because air involved among the magnetic sheets is a quite small amount.
[0020]According to this invention described above, the magnetic sheet with an extremely high quality in appearance as well as magnetic characteristics can be manufactured with high productivity.

Problems solved by technology

However, in the RFID system, when other metal objects surround the transponder, problems may occur in its communication in response to their influence.
In an electromagnetic induction type, when other metal objects surround the transponder, a resonant frequency shifts and flux changes occur due to inductance change in response to the influence, and this leads to a failure to ensure electric power.
Although the ferrite is known as a magnetic material suitable for rendering the device lighter, the ferrite raises a problem on being fragile and extremely low-impact-resistance because the ferrite is a brittle material in a case where used as a magnetic sheet for a mobile communication equipment.
In a conventional method for manufacturing magnetic sheet, however, there raise problems such that the plural magnetic sheets are accumulated in a misaligned state and that the manufacturing steps becomes long with poor productivity, because the conventional method is accompanied with a step of accumulating plural sheets after separating the magnetic sheet from PET for releasing.
Therefore, the magnetic sheets manufactured by such a manufacturing method raise a problem that under a high-temperature environment or a high temperature and high humidity environment, air involved in the magnetic sheets expands to make the thickness of the magnetic sheets thicker as a change.
Furthermore, in the conventional method for manufacturing magnetic sheets, there raises a problem to render the appearance worse due to ejection of air involved among the magnetic sheets at the surface where the magnetic sheets are compressed at high pressure to make magnetic characteristics better.
On the contrary, where the appearance is tried to be not worse, there still raises a problem that the magnetic characteristics may be deteriorated due to a failure in providing a high pressure at the time of compression.
In the conventional method for manufacturing magnetic sheets, there raises a problem that the magnetic paint may not be coated smoothly due to blurs to render the thickness in the surface more uneven where the magnetic paint is coated further on the formed magnetic sheet.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0051]A magnetic paint was coated on a PET (polyethylene terephthalate) for release; a magnetic sheet was formed upon drying at 115 degrees Celsius; and another magnetic paint was further coated thereon and dried at 115 degrees Celsius. Those steps were repeated, and a magnetic sheet equivalent to the six layered magnetic sheets was obtained. Subsequently, the obtained magnetic sheet was compressed by being fed ten times between rollers set at 110 degrees Celsius with linear pressure 3.3 kgf / cm2 to discharge air, and was further compressed at 150 degrees Celsius and 5.9 kgf / cm2 to obtain a magnetic sheet as the final product. As a result, the magnetic sheet had a good appearance and magnetic characteristics, as well. The magnetic sheet received quite less changes in thickness and magnetic characteristics though left stably for 168 hours under the high temperature environment of 85 degrees Celsius as well as under the high temperature of 60 degrees Celsius and high humidity environme...

example 2

[0052]A magnetic paint was coated on a PET for release; a magnetic sheet was formed upon drying at 115 degrees Celsius; and another magnetic paint was further coated thereon and dried at 115 degrees Celsius. Those steps were repeated, and a magnetic sheet equivalent to the six layered magnetic sheets was obtained. Subsequently, the obtained magnetic sheet was compressed by being fed ten times between rollers set at 110 degrees Celsius with linear pressure 3.3 kgf / cm2 to discharge air, and was further compressed at 150 degrees Celsius and 6.2 kgf / cm2 to obtain a magnetic sheet as the final product. That is, in this Example 2, the material of the magnetic paint was different from that in Example 1, and the magnetic sheet was compressed with a higher pressure than Example 1. As a result, the magnetic sheet had a good appearance and magnetic characteristics, as well, though compressed with a higher pressure than Example 1. The magnetic sheet received very quite less changes in thickness...

example 3

[0053]A magnetic paint was coated on a PET for release; a magnetic sheet was formed upon drying at 115 degrees Celsius; and another magnetic paint was further coated thereon and dried at 115 degrees Celsius after the magnetic sheet was compressed by being fed one time between rollers set at 110 degrees Celsius with linear pressure 3.3 kgf / cm2. Those steps were repeated, and a magnetic sheet equivalent to the six layered magnetic sheets was obtained. Subsequently, the obtained magnetic sheet was compressed by being fed ten times between rollers set at 110 degrees Celsius with linear pressure 3.3 kgf / cm2 to discharge air, and was further compressed at 150 degrees Celsius and 6.4 kgf / cm2 to obtain a magnetic sheet as the final product. That is, in this Example 3, the magnetic sheet was compressed with a higher pressure than Example 2 by setting a compressing step after coating and drying the magnetic paint. As a result, the magnetic sheet had a good appearance and magnetic characterist...

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Abstract

In manufacturing a magnetic sheet, the magnetic sheet is formed by applying on a prescribed substrate a magnetic paint made from a mixture of at least flat soft magnetic powder and polymeric binder dissolved in a solvent and drying the magnetic paint. Subsequently, the magnetic paint is further coated on the magnetic sheet formed by drying the magnetic paint and is dried. Thus, an extremely high quality magnetic sheet is made with high productivity.

Description

TECHNICAL FIELD[0001]The present invention relates to a method for manufacturing a magnetic sheet suitable for IC cards or IC tags reducing electromagnetic wave noises and to a magnetic sheet manufactured by this manufacturing method.BACKGROUND OF THE INVENTION[0002]Recently, a system performing individual managements, or so-called RFID (Radio Frequency IDentification), has been introduced to the various industries. This RFID system is a technology to make wireless communications between a small non-contact integrated circuit (hereinafter referred to as “IC”) device storing various data readable and writable and having telecommunication function, so-called a transponder, and a predetermined reader / writer and to read and / or write data without any contacting the transponder. Specifically, in the RFID system, on the basis of the principle of electromagnetic induction, in accordance with the release of the magnetic flux from a loop antenna on a reader / writer side, released flux is magne...

Claims

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Application Information

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IPC IPC(8): H01F1/12B05D5/12
CPCG06K19/07771H05K9/0083H01F41/16H01F1/26H01F1/147H01F1/44H01F41/00H05K9/00
Inventor ARAMAKI, KEISUKE
Owner DEXERIALS CORP